In a large pot of boiling salted water, cook green beans until crisp-tender, about 4 minutes. Drain and rinse under cool water to stop the cooking. Meanwhile, in a large bowl, whisk together lemon juice and oil. Stir in tomatoes, onion, chickpeas, and lemon zest. Add feta and parsley and stir to combine. Season with salt and pepper. Arrange green beans on a serving platter and top with tomato mixture.